Is Excessive Weight Gain After Ablative Treatment of Hyperthyroidism due to Inadequate Thyroid Hormone Therapy?

Abstract

There is controversy about the correct dose and form of thyroid hormone therapy for patients with hypothyroidism. Despite restoration of serum thyrotropin (TSH) concentrations to normal, many patients complain of excessive weight gain. We have compared weight at diagnosis of hyperthyroidism with that when euthyroid, evidenced by a stable, normal serum TSH concentration, with or without thyroxine (T4) replacement therapy, in patients treated with an 18-month course of antithyroid drugs (43 patients), surgery (56 patients), or 13I (34 patients) for Graves' disease. In addition, weights were recorded before and after treatment of 25 patients with differentiated thyroid carcinoma by total thyroidectomy, 131I, and long-term T4 suppressive therapy, resulting in undetectable serum TSH concentrations. Mean weight gain in patients with Graves' disease who required T4 replacement therapy following surgery was significantly greater than in those of the same age, sex, and severity of hyperthyroidism rendered euthyroid by surgery (3.9 kg) (p < 0.001) or at the end of a course of antithyroid drugs (4.1 kg) (p < 0.001). Weight gain was similar in those requiring T4 replacement following surgery or 131T therapy (10.4 versus 10.1 kg). In contrast, ablative therapy combined with suppression of TSH secretion by T4 in patients with differentiated thyroid carcinoma did not result in weight gain. The excessive weight gain in patients becoming hypothyroid after destructive therapy for Graves' disease suggests that restoration of serum TSH to the reference range by T4 alone may constitute inadequate hormone replacement.

Weight Changes in Euthyroid Patients Undergoing Thyroidectomy

“…This has been reported in previous studies (14,17). An association between serum TSH and weight gain has also been previously reported (24).…”

“…Certainly, hypothyroidism after thyroidectomy has been associated with weight gain (13)(14)(15)17). However, in our recently thyroidectomized patients, there was no intervening period of hypothyroidism.…”

“…The weight gain averaged 3.7 kg per year 1 in one of these studies (13) and 6 kg per year in another (15). In the third study, there was a weight gain of about 4 kg in those who were simply rendered euthyroid, compared with about 10 kg in those who had intervening hypothyroidism (14). Another study showed that treatment of hypothyroidism was only associated with loss of body water, not loss of fat mass (16).…”

“…Most weight gain occurred within 3 months of surgery and was not reversed with a return to euthyroidism (12). Other studies show significant weight gain after treatment of hyperthyroidism, with significantly greater weight gain when thyroidectomy was the treatment employed (13), and association between development of iatrogenic hypothyroidism and the subsequent weight gain (13)(14)(15). The weight gain averaged 3.7 kg per year 1 in one of these studies (13) and 6 kg per year in another (15).…”

“…Another study showed that treatment of hypothyroidism was only associated with loss of body water, not loss of fat mass (16). Patients who were maintained on thyroid hormone suppression therapy had some limitation of their weight gain (14,17).…”